Figure 1.

The power spectrum of the receptor state P_n(ω) for c = 0.4 μM. The simulation results (black circles) agree well with the theoretical prediction of Eq. 13 (solid red line). At high frequencies ω > 1/τ_m = D/σ², the effect of diffusion is negligible and the receptor dynamics is that of a Markovian switching process with intrinsic rates k_ac and k_d (dashed red line), while at low frequencies it is that of a Markovian switching process with effective rates k_onc and k_off, respectively (solid gray line). The zero-frequency limit determines the precision of the concentration estimate. Parameters: $\overline{n}=0.5$, D = 1 μm² s⁻¹, σ = 10 nm, L = 1 μm, and k_a = 552 μM⁻¹ s⁻¹. To see this figure in color, go online.